SATELLITE SYSTEMS

Military satellite projects were added to the mission of the Western Development Division in the mid-1950's and came to play an increasingly important role in the activities of the Division's successors. The first satellite program was known as the Military Satellite System (WS 117L), and the Division was given responsibility for it in February 1956. WS 117L was to be a family of separate subsystems that could carry out different missions, including photo reconnaissance and missile warning. By the end of 1959, WS 117L had evolved into three separate programs--the Discoverer Program, the Satellite and Missile Observation System (SAMOS), and the Missile Detection Alarm System (MIDAS). Discoverer and SAMOS were to carry out the photo reconnaissance mission, and MIDAS was to carry out the missile warning mission.

The Discoverer program aimed at developing a film-return photo reconnaissance satellite. The satellite would carry a camera that took pictures from space as it passed over the Sino-Soviet bloc. Film from the camera would be deorbited in a capsule. A parachute would be deployed to slow the descent of the capsule, and the capsule would be recovered either in mid-air or in the ocean. It should be emphasized that the photo reconnaissance mission of Discoverer was not revealed to the public at the time. Discoverer was presented as an experimental program to develop and test satellite subsystems and explore environmental conditions in space.


President Eisenhower inspecting the capsule from Discoverer XIII-- the first object ever ejected from an orbiting satellite and subsequently recovered. Standing behind Eisenhower from left to right: Col Lee Battle, Discoverer program director; Gen Curtis LeMay, Air Force Vice Chief of Staff; Lt Gen Bernard Schriever, commander of ARDC; Dudley Sharp, Secretary of the Air Force; unidentified CIA official; and Gen Thomas White, Chief of Staff of the Air Force.

A C-119 aircraft about to recover an object in the same manner as it would a Discoverer capsule. After the capsule was separated from the satellite, a retro-rocket would be fired to put it into a descent trajectory. Two parachutes-- a drogue chute and a main chute-- would later be deployed to slow the descent of the capsule. An airplane would then fly across the top of the descending parachute and catch it in a trapeze-like framework. The capsule would then be winched aboard the plane.


The Discoverer Program carried out 38 launches and achieved many breakthroughs in the process. Discoverer I, launched in February 1959, was the world's first polar orbiting satellite. Discoverer II, launched in April 1959, was the first satellite to be stabilized in orbit in all three axes, to be maneuvered on command from the earth, to separate a reentry vehicle on command, and to send its reentry vehicle back to earth. Discoverer XIII, launched in August 1960, ejected a capsule that was subsequently recovered in the Pacific Ocean--the first successful recovery of a man-made object ejected from an orbiting satellite. Discoverer XIV, launched later the same month, also ejected a capsule, and it was recovered in mid-air northwest of Hawaii by a C-119J aircraft--the first successful aerial recovery of an object returned from orbit. The capsule of Discoverer XIV was the first to return film from orbit, inaugurating the age of satellite reconnaissance. Satellite reconnaissance filled a crucial need, because President Eisenhower had suspended aerial reconnaissance of the Soviet Union just three months earlier, after the Soviets had shot down the U-2 spy plane piloted by Francis Gary Powers.

The Discoverer Program was officially ended after the launch of Discoverer XXXVIII in February 1962. In reality, however, it continued until 1972 under the secret code name CORONA--the name by which Discoverer was known in the intelligence community. CORONA's first major accomplishment was to provide photos of Soviet missile launch complexes. It also identified the Plesetsk Missile Test Range, north of Moscow, and provided information as to what missiles were being developed, tested, and deployed. These and other accomplishments were revealed when the CORONA Program was declassified in February 1995.

SAMOS--the second program that evolved from WS 117L--aimed at developing a heavier reconnaissance satellite that would be launched by an Atlas booster rather than the Thor used to launch the Discoverer. SAMOS had two launches--one in October 1960, which failed, and one in January 1961, which was successful. In 1962, a veil of secrecy was drawn across the SAMOS program, and the Air Force stopped releasing information about it. Unlike Discoverer (AKA Corona), it has never been declassified.

The MIDAS program--the third offshoot of WS 117L--aimed at developing a satellite that would carry an infrared sensor to detect hostile ICBM launches. The first MIDAS satellite, launched in February 1960, failed to achieve orbit. MIDAS II, launched in May 1960, did achieve orbit, but its telemetry system failed two days after launch. MIDAS III, successfully launched in July 1961, also achieved orbit and was the heaviest US satellite launched up to that time. As was the case with SAMOS, a veil of secrecy was drawn across the MIDAS program in 1962. However, MIDAS eventually evolved into the Defense Support Program (DSP), and the DSP mission was declassified following the Persian Gulf war of 1991. Today, the satellites, ground stations, and mobile ground terminals of DSP perform MIDAS's original mission of detecting and reporting on hostile missile launches.


The current version of the DSP satellite.


In addition to reconnaissance and missile warning, satellites have been developed to serve a number of other purposes, among which are nuclear surveillance, weather observation, navigation, and communication. Nuclear surveillance was carried out by six pairs of Vela satellites placed into orbit between October 1963 and April 1970. These satellites were used primarily to monitor the 1963 Nuclear Test Ban Treaty, but they also provided important scientific data on solar flares and on other radiation that could affect man's safety in space.


A pair of Vela satellites stacked in their launch configuration.


Weather observation is the mission of the Defense Meteorological Satellite Program (DMSP), which maintains a constellation of at least two weather satellites in polar orbits about 450 miles above the earth. Space Systems Division began development and deployment of weather satellites and associated ground stations and weather terminals during the 1960's. The system made its first major contribution during the southeast Asian conflict, when data from weather satellites was used to plan air operations. The existence of a military weather satellite system was secret during the war but was declassified in 1973. Since the Vietnam era, all elements of the system have been upgraded repeatedly. The Block 5D-2 satellites currently in orbit carry primary sensors that provide images of cloud cover over the earth's surface during both day and night, and they also carry other sensors that provide additional types of data on weather and on the space environment. All this information is supplied to the armed services to support military operations and also to the National Oceanic and Atmospheric Administration to support civilian weather forecasting. DMSP satellites have shown themselves to be an economical and effective means of detecting and tracking tropical storms, especially in the western Pacific.


Artist's conception of a DMSP Block 5D-2 satellite in orbit. The satellite's primary sensor scans the earth's surface, moving back and forth along a swath 1600 nautical miles wide. (The sensor's ground track is shown in the photo.) Visual and infrared detectors inside the sensor pick up imagery of cloud cover on the earth's surface.

Pictures of Typhoon June over the Pacific, taken by a DMSP satellite in November 1975. The picture on the left was taken by the sensor's visual detector; the one on the right, by its infrared detector.


The navigation mission is carried out by the Global Positioning System (GPS). The system consists of satellites that broadcast navigation signals to the earth, a control segment that maintains the accuracy of the signals, and user equipment that receives and processes the signals. By processing signals from the nearest four satellites, a user set is able to derive the location of each satellite and its distance from each one, and from that information, it derives its own location in three dimensions.


Evolution of the GPS satellite, showing (from top to bottom) the Block I, the Block IA, the Block II, and the Block IIA. The Block I and Block IA were R&D models; the Block II and IIA are production models intended for operational use.


GPS had two ancestors--a technology program called 621B, started by SAMSO in the late 1960s, and a parallel program called Timation, undertaken by the Naval Research Laboratory in the same period. 621B envisioned a constellation of 20 satellites in synchronous inclined orbits, while Timation envisioned a constellation of 21 to 27 satellite in medium altitude orbits. In 1973, elements of the two programs were combined into the GPS concept, which employed the signal structure and frequencies of 621B and medium altitude orbits similar to those proposed for Timation.

The Deputy Secretary of Defense authorized the GPS program to start in December 1973. The system was acquired in three phases--validation, development, and production. During the validation phase, Block I navigation satellites and a prototype control segment were built and deployed, and advanced development models of various types of user equipment were built and tested. During the development phase, additional Block I satellites were launched to maintain the initial satellite constellation, a qualification model Block II satellite was built and tested, and manufacture of additional Block II satellites was initiated. In addition, an operational control segment was activated, and prototype user equipment was developed and tested. During the production phase, a full constellation of 24 Block II and IIA satellites was deployed, and user equipment was produced and put into operation--i.e., issued to foot soldiers and installed in ships, submarines, aircraft, and ground vehicles. The full constellation of Block II and IIA satellites was completed in March 1994, allowing the system to attain full operational capability in April 1995. The system is able to support a wide variety of operations, including aerial rendezvous and refueling, all-weather air drops, instrument landings, mine laying and mine sweeping, anti-submarine warfare, bombing and shelling, photo mapping, range instrumentation, rescue missions and satellite navigation.

Various satellite systems have been developed for communication purposes, and the first of these was fielded by the Initial Defense Communications Satellite Program (IDCSP). The program began in 1962, following cancellation of an earlier, unsuccessful program called Project Advent. The IDCSP system consisted of small, 100 pound satellites launched in clusters, and a total of 26 such satellites were placed into orbit in four launches carried out between June 1966 and June 1968. The IDCSP provided an experimental but usable worldwide military communications system for the Defense Department until a more sophisticated system could be developed.


A group of eight IDCSP satellites in a dispenser being checked out prior to launch. The IDCSP satellites were small and very simple, with no batteries and no active attitude control system.

Artist's conception of eight IDCSP satellites being ejected one at a time from their dispenser into near-synchronous orbits.


That more sophisticated system was known as the Defense Satellite Communications System, Phase II (DSCS II). The DSCS II satellites were much larger than the IDCSP satellites and offered increased communications capacity, greater transmission strength, and longer lifetimes. In addition to horn antennas for wide area coverage, they had dish antennas that were steerable by ground command and provided intensified coverage of small areas of the earth's surface. The DOD gave the go-ahead for development of the DSCS II satellite in June 1968. The first two satellites were put into geosynchronous orbits in November 1973. Two launch failures delayed completion of the satellite network, but by January 1979 the full constellation of four satellites was in place and in operation. A total of 16 DSCS II satellites were built and launched during the life of the program, with the last launch occurring in 1989.


Artist's conception of a DSCS II satellite in orbit.


In 1973, planning began for the Defense Satellite Communications System, Phase III (DSCS III). DSCS III satellites carry multiple beam antennas to provide flexible coverage and resist jamming, and they offer six active communication channels rather than the four offered by DSCS II. The first DSCS III satellite was successfully launched in October 1982, and a full constellation of five DSCS III satellites was completed in July 1993.


A DSCS III satellite in an anechoic (echo-free) test chamber at the contractor's facility.


DSCS satellites were developed to serve users who transmit message traffic at medium to high data rates using relatively large ground terminals. However, satellites were also needed to serve users who transmit at low to medium data rates, using small, mobile or transportable terminals. During the 1960's, experimental satellites were placed into orbit to test technology that might perform this tactical communications mission. Lincoln Experimental Satellites 5 and 6, launched in July 1967 and September 1968, were solid-state, ultra high frequency communication satellites built by Lincoln Laboratory. The 1,600 pound Tactical Communications Satellite, launched in February 1969, operated in both ultra high frequency and super high frequency and tested the feasibility of communications with small, mobile, tactical communications equipment that could be used by ground, naval, and air forces. In July 1970, an initial operational capability for tactical communications was established, using the Tactical Communications Satellite and Lincoln Experimental Satellite 6.


The Tactical Communications Satellite (TACSAT I) in the contractor's facility.


These experimental satellites paved the way for the Fleet Satellite Communications System (FLTSATCOM), the first operational system serving tactical users. The Navy managed the overall program, but SAMSO managed acquisition of the satellites. Development of FLTSATCOM was authorized in 1971, and five satellites were launched between February 1978 and August 1981. Four achieved orbit and went into operation, but one was damaged during launch and never became operational. Three replenishment satellites were launched between December 1986 and September 1989. Two reached orbit, but one was lost when its booster was hit by lightning.


Artist's conception of the FLTSATCOM satellite in orbit.


In addition to the long-haul users served by DSCS and the tactical users served by FLTSATCOM, there was a third group of users--the nuclear capable forces--who could be satisfied with very low data rates but required high availability, worldwide coverage, and the maximum degree of survivability. The Air Force Satellite Communications System (AFSATCOM) was developed to serve their needs and allow the Air Force to command and control its strategic forces. The space segment of the system relied on transponders (receiver/ transmitters) placed on board FLTSATCOM satellites and other DOD spacecraft. The space segment of AFSATCOM was declared operational in April 1978, and the terminal segment attained initial operational capability in May 1979.

The newest space communications system acquired by SMC is Milstar. Milstar I satellites carry a low data rate payload that provides worldwide, survivable, highly jam-resistant communications for the National Command Authority and the tactical and strategic forces. Space Division awarded concept validation contracts for the satellite and mission control segment of Milstar I in March 1982 and a development contract in February 1983. The first Milstar I satellite was successfully launched in February of this year. In October 1993, SMC awarded a contract for development of the Milstar II satellite, which will carry both low and medium data rate payloads. The addition of the medium data rate payload will greatly increase the ability of the tactical forces to communicate within and across theater boundaries.


Artist's conception of the MILSTAR satellite in orbit.


The communications satellites discussed up to this point were all acquired for the US military, but other communications satellites were acquired for the United Kingdom and the North Atlantic Treaty Organization. The British Skynet program began in 1966. The first of two Skynet I satellites was placed into orbit in November 1969 and provided the United Kingdom with its first military communications satellite system. The second Skynet satellite was launched from Cape Canaveral in August 1970, but a malfunction in the launch vehicle caused permanent loss of contact with the satellite. In 1970, SAMSO and the United Kingdom began development of a more advanced Skynet II satellite system. The first Skynet II satellite was launched in January 1974, but a malfunction in the launch vehicle again caused the loss of the satellite. The second Skynet II satellite, launched in November 1974, attained orbit successfully and was turned over to the United Kingdom in January 1975.


A Skynet I satellite at the contractor's facility.


Development of the NATO satellites began in April 1968, with the initial series of satellites being known as NATO II. One NATO II satellite was placed in orbit in March 1970 and another in February 1971. Both the Skynet and NATO satellites were designed to be compatible and usable with each other and with the Defense Satellite Communications System. Work on a more advanced system, NATO III, began in 1973, and three NATO III satellites were successfully launched between 1976 and 1978. The constellation was replenished in November 1984, when a fourth satellite was successfully launched.


Artist's conception of the NATO III satellite in orbit.